Ferrous and non-ferrous castings are widely used in, for example, the automotive industry. The casings can be produced in high volume by pouring the molten metal into a series of sand-based molds and then letting the metal cool and harden. The fresh, i.e., newly made, castings are then removed from the mold and further processed by, for example, removing any unwanted transient projections resulting from the casting procedure.
Traditionally, these unwanted projections were knocked off manually with a hammer or a cold chisel and hammer. Modern production methods emphasize mechanized systems for rapidly removing the unwanted projections from castings on a volume basis and a rotary mace with pivotable hammers has been used commercially in the automotive industry to process castings such as cast iron engine heads.
The rotary mace previously used is a rotatable device usually made largely or entirely of steel, having a number of hammers ordinarily formed of tool steel, each pivotably attached by means of an eye at the end of the shank of the hammer through which is passed a steel clevis having notched legs that are locked into a face of a polygonal rotatable steel body called a hub. Each hub face is provided with the requisite number of boreholes extending radially inward into the face to receive the notched legs of the clevises. The hub is also bored axially from the ends thereof to provide a sufficient number of boreholes for retaining pins used to secure the legs of the clevises. Each axial borehole lies in a direction approximately parallel to the axis of the hub and adjacent to a hub face, and transversely to the radial borehole receiving a leg of one of the clevises so as to intersect only a portion of a clevis leg-receiving borehole. A pin is inserted through each such axially directed bore to intercept an aligned notch in a clevis leg, thus providing a retaining means for the clevis. The pins have usually been retained in the hub by bolting a ring shaped cover piece or collar to each end face of the hub so that the ring shaped pieces cover the pin bore openings after the pins have been inserted. Fresh castings are passed appropriately near the rotating rotary mace so that the pivotable hammers impact the unwanted projections on the castings and knock them off. Durable, resilient plastic bumpers or pads are attached to the circumferential hub faces on either side of the hammers along a circumferential line to prevent the pivoting hammers from damaging the hub as the hammers bounce or recoil off a casting during rotation of the mace.
The rotary mace was a successful development over manual operations. However, it is in need of improvement. Boring the boreholes in the hub parallel to the axis thereof to receive the locking pins for the clevis legs is expensive because of the linear length of the holes required to hold an array of clevises to hold a row of hammers as desired. This problem could be lessened by making the hub in narrow or somewhat discate segments, but then it would be necessary to bolt the segments together along the common axis, increasing the complexity of the hub, so this answer was not widely adopted. Replacing worn out or badly deformed hammers from a single hub carrying a plurality of hammers required driving out the elongated locking pins which are often wedged fast in their bores by accumulated dirt and sand picked up during normal operations. Driving too hard on a wedged pin often upset the driven end of the pin to such a degree that drilling the pin out would be about the only means of recovering the hub to place it back in service. Occasionally a bumper would be dislodged from the hub and the hub face would be promptly damaged, necessitating expensive refinishing or repair before a replacement bumper could be installed.